1. Field of the Invention
The present invention relates to an image processing apparatus applied to a case of recording image data for use in forming images on sheets, as history information, a method of controlling the image processing apparatus, and a computer-readable storage medium storing a program for implementing the method.
2. Description of the Related Art
Recently, not only the full-color printing method in which electrophotographic printing is performed using four color toners (cyan (C), magenta (M), yellow (Y), and black (B)), but also a multi-color printing method additionally using a special toner has attracted attention.
A bill/check centralized issuing system for financial institutions is known as a special toner-using printing method which has already become commercially available. This is a method in which an image is formed using clear toner on a sheet having an image formed thereon by the general electrophotographic printing method. According to this method, information for certifying that a printout is an original is printed, which makes it possible to visualize normally invisible printed information by ultraviolet radiation to thereby show that the printout is not a replica produced by forgery or copying.
Although in the above-mentioned example, a clear-toner layer is superimposed on a monochrome printout, the use of clear toner makes it possible to provide the same advantageous effects for color printing as well. As far as color printing is concerned, there has also been proposed a technique which makes it possible to control the glossiness of a print surface using clear toner (see e.g. Japanese Patent Laid-Open Publication No. H10-55085).
To print a clear-toner image on an ordinary image in superimposed relation, there is employed the following known technique: Before rasterizing a form image by an image processing apparatus for printing, and printing the form image on a to-be-printed image, in superimposed relation, a computer generates information for activating the function of applying clear toner onto the form image alone in superimposed relation and information on positions where the clear toner is to be superimposed. Thereafter, the generated information is converted into PDL (Page Description Language) data as attribute data together with the to-be-printed image data, and is sent to the image processing apparatus. The image processing apparatus prints the to-be-printed image on a sheet using color toners and at the same time superimposingly prints a clear-toner image on the printed print image according to the attribute data.
On the other hand, with widespread use of image processing apparatuses, anyone can easily print various information or copy originals using an image processing apparatus. However, there is a fear that improvement in user-friendliness of image processing apparatuses in printing and copying might increase possibility of information leakage (printing or copying of secret information).
To prevent information leakage, there is provided a function of accumulating all image data printed or read from originals in a recording device whenever printing or copying is performed by each image processing apparatus, and recording a job history storing pieces of information each indicative of what kind of processing was carried out by whom, and when and where. This function is advantageous in that an administrator can make use of the function to check on the accumulated image data to thereby investigate and trace afterwards which image processing apparatus processed leaked information and an associated original.
However, the above-described conventional technique of superimposingly printing a clear-toner image on an ordinary image suffers from the following problems:
When the image processing apparatus receives clear-toner attribute data as position information indicative of where to apply clear toner, together with data of a to-be-printed image, from the computer, it performs control such that clear toner is applied based on the attribute data. In this case, the attribute data cannot be synthesized as image data with to-be-printed image data. The to-be-printed image data is formed on a sheet using toner, whereafter clear-toner image is superimposed on a predetermined portion of the toner image based on the attribute data.
On the other hand, in a case where printing is performed based on image data while using the function of generating image data for job history and recording the generated data in a recording device for security, the image data is stored as job history information. However, the clear-toner attribute data, which is not image data, is not stored as job history information.